Static ignition timing instrument



Dec. 9, 1969 F. J. TRULSON STATIC IGNITION TIMING INSTRUMENT Filed Feb. 25, 1966 INVENTOR. FREDERICK J. TRULSON J ATTORNEY United States Patent 3,483,544 STATEC iGNiTlGN TIMING INSTRUMENT Frederick J. Truison, Detroit, Mich, assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Feb. 25, 1966, Ser. No. 530,011 int. Cl. GtlSb 29/00, 21/00 US. Cl. 34i)213 3 Ciaims ABSTRACT OF THE DISCLOSURE An instrument for timing the ignition system of an internal combustion engine while the engine is at rest. The inverting input circuit of an operational amplifier is connected across the breaker points of an associated ignition distributor. The output of the operational amplifier is connected across the base-emitter electrodes of a first transistor, selected to be of the type which will conduct in response to the polarity of the amplifier output potential while the points are closed, having an indicating lamp connected in series with the collector-emitter electrodes thereof and a source of operating potential whereby the associated lamp is energized while the breaker points are closed. An opposite polarity input signal is impressed across the input circuit of the operational amplifier upon the opening of the ignition breaker points as the distributor is manually rotated, consequently, the polarity of the operational amplifier output signal is reversed, a condition which extinguishe's the first transistor. With this transistor extinguished, an operating potential of the correct polarity relationship is applied across the base-emitter electrodes of a second transistor having an indicating lamp connected in series with the collector-emitter electrodes thereof and a source of operating potential. Therefore, this device conducts to energize the lamp which indicates that the breaker points have opened.

This invention relates to instruments for timing the ignition system of internal combustion engines and, more specifically, to a static ignition timing instrument for internal combustion engines.

The most generally accepted method of timing the ignition system of an internal combustion engine is to adjust the ignition distributor setting while the engine is in the running mode.

The advantages of an instrument with which the ignition timing setting of the distributor of an internal combustion engine may be accurately adjusted while the engine is not running and which, therefore, obviates the requirement of timing lights and the necessity for the mechanic to be in close proximity to a running engine, is apparent.

It is, therefore, an Object of this invention to provide an improved instrument for timing the ignition system of internal combustion engines.

it is another object of this invention to provide a static ignition timing instrument for internal combustion engines with which the proper setting of the distributor timing adjustment may be made without the engine running.

in accordance wih this invention, a static ignition timing instrument for internal combustion engines is provided wherein a transfer of energization from a first indicator circuit to a second indicator circuit, in response to a signal produced by an electrical circuit device of the type responsive to signals upon the input circuit thereof to produce signals of opposite polarity upon the output circuit thereof, indicates that the ignition timing setting of the distributor of an internal combustion engine is properly adjusted.

For a better understanding of the present invention, together with additional objects, advantages and features 3,483,544 Patented Dec. 9, 1969 thereof, reference is made to the following description and accompanying single figure drawing.

Most internal combustion engine ignition system distributors are of either the conventional breaker contact type or the magnetic pulse generator type. The novel static ignition timing instrument of this invention may be employed with either type ignition system distributor.

In the conventional breaker contact type distributors, electrical breaker contacts are opened and closed by a breaker cam having a plurality of lobes, each corresponding to a cylinder of the engine, which is rotated in timed relationship with the engine. The ignition system circuitry associated with breaker contact type distributors is arranged to produce the high voltage ignition pulse necessary to fire each cylinder upon each opening of the breaker contacts by a lobe on the breaker cam.

In the magnetic pulse generator type distributors, a rotor member of magnetic material having a plurality of projections or teeth, each corresponding to a cylinder of the engine, is driven in timed relationship with the engine within a magnetic pickup assembly. Each projection or tooth on the rotor member varies the reluctance of a magnetic circuit in the magnetic pickup assembly which results in an alternating current ignition synchronizing signal being induced in an associated pickup coil. The ignition system circuitry associated with magnetic pulse generator type distributors is arranged to produce the high voltage ignition pulse necessary to fire each cylinder upon each reversal from a selected one polarity to the opposite polarity, or cross-over, of the induced ignition synchronizing signal.

The novel static ignition timing instrument of this invention detects and indicates the moment of opening of the breaker contacts of conventional breaker contact type distributors and the cross-over of the induced ignition synchronizing signal of magnetic pulse generator type distributors.

As is well known in the art, one cylinder of an internal combustion engine is selected as the reference cylinder and the ignition system is timed relative to that cylinder. When the piston within that cylinder is at the position at which ignition within that cylinder is to occur, a timing mark located upon a rotating member of the engine, such as the flywheel, is aligned with an associated timing mark located upon an adjacent stationary member of the engine, such as the bell housing. Therefore, the' breaker contacts of a conventional breaker contact type distributor should open and the cross-over of the ignition synchronizing signal produced by magnetic pulse generator type distributors should occur when the timing marks of the engine are in alignment.

To use the novel static timing instrument of this invention the distributor is mounted on the engine, the timing marks of the engine to be timed are placed in alignment, the static ignition timing instrument is properly connected to the distributor, as will be explained in detail later, and the distributor housing is rotated, preferably by hand.

Without the engine running, the static ignition timing instrument of this invention will detect and indicate the moment the breaker contacts of conventional breaker contact type distributors open or the moment of crossover of the induced ignition synchronizing signal of magnetic pulse generator type distributors.

Referring to the figure, the static ignition timing instrument of this invention is set forth in schematic form. It may be noted that several points are labeled with electrical polarities. The source of direct current potential for use with this instrument should be of the type which provides two potentials of substantially equal magnitude and opposite polarity, relative to point of reference or ground potential 5. As power supplies of this type are commercially available items well known in the art and form no part of this invention, in the interest of reducing drawing complexity, it has not been illustrated in the figure. The source of direct current potential will hereinafter be referred to as the power supply.

As point of reference or ground potential is the same point electrically throughout the system, it has been illustrated by the accepted symbol and referenced by the numeral 5 in the figure. Throughout the following specification, specific electrical potential polarities will be designated. Except as otherwise noted, these electrical potential polarities will be in respect to point of reference or ground potential 5.

To accommodate ignition distributors of both the conventional breaker contact and magnetic pulse generator types, respective input circuitry is provided which may be conventional electrical terminals 16 and 11 and 12 and 13 or any other arrangement suitable for external electrical connections. Terminals 11 and 13 are shown to be connected to point of reference or ground potential 5, therefore, these two terminals may be combined into a common terminal.

To produce an electrical signal upon the opening of the breaker contacts of conventional breaker contact type distributors and at the cross-over of the signal induced in the pickup winding of magnetic pulse generator type distributors, a first circuit means, having input and output circuitry, of the type responsive to a signal upon the input circuitry to produce a signal of opposite polarity upon the output circuitry, is provided. In the figure, this circuit device is schematically illustrated as a conventional operational amplifier 15 and its associated circuitry. The input circuit may include a terminal 16 and ground 5 and the output circuit may include a terminal 17 and ground 5. Alternate acceptable electrical connections or connectors may be substituted for terminals 16 and 17.

Operational amplifiers are high gain amplifiers which produce an output signal of a magnitude much greater than and of a polarity opposite to an electrical signal present upon the input circuit and are extremely sensitive to changes of electrical polarity upon the input circuit. Operational amplifiers are commercially available items which are well known in the art, consequently, in the interest of reducing drawing complexity, it has been shown in block form in the figure. It is to be specifically understood that alternate circuit arrangements having similar electrical characteristic may be employed without departing from the spirit of the invention.

To selectively connect the instrument input circuitry comprising terminals 10 and 11 and terminals 12 and 13 to the input circuit of operational amplifier 15, a single pole, double throw selector switch 18 having a movable contact 19 connected through current limiting resistor 22 to terminal 16 and two stationary contacts and 21, is provided.

To indicate the opening of the breaker contacts of conventional breaker contact type distributors and the cross-over of the signal induced in the pickup winding of magnetic pulse generator type distributors, a first indicator circuit which may be energized in response to a selected one polarity signal present upon the output circuit of operational amplified 15 and deenergized in response to an opposite polarity signal present upon the output circuit of operational amplifier 15 and 'a second indicator circuit which may be energized in response to the deenergization of the first indicator circuit, is provided.

In the figure, the first indicator circuit includes a type PNP switching transistor having the usual base 31, emitter 32 and collector 33 electrodes and a conventional electric lamp 25 and the second indicator circuit includes a type PNP switching transistor having the usual base 41, emitter 42 and collector 43 electrodes and conventional electric lamp 26.

An interruption of the rotation of the housing of the distributor may produce a false indication of a breaker contact opening or an induced pulse cross-over. To preclude this possibility, a circuit is provided to produce a feedback signal of a polarity the same as the last signal present upon the input circuit of operational amplifier 15 in response to a signal upon the output circuit of operational amplifier 15.

This circuit includes type PNP transistor 50 having the usual base 51, emitter 52 and collector 53 electrodes and the associated circuitry which will be explained in detail later in this specification.

To return the feedback signal to the input circuit of operational amplifier 15, a feedback circuit is provided which includes movable contact 36 of potentiometer 35. line 37, resistor 38 and line 39.

Connected across the positive and negative polarity terminals of the power supply is a voltage divider network comprising the serie combination of resistors 44, 45 and 46. The instrument input terminal 10' is connected to junction 47 between resistors 44 and 45 and stationary contact 21 of selector switch 18 is connected to junction 48 between resistors 45 and 46. Instrument input terminal 12 i connected to stationary contact 20 of selector switch 18 through line 49. Therefore, for use with conventional breaker contact type distributors, movable contact 19 of selector switch 18 is closed to stationary contact 21 and for use with magnetic pulse generator type distributors, movable contact 19 of selector switch 18 is closed to stationary contact 20.

Also connected across the positive and negative polarity terminals of the power supply in another voltage divider network comprising the series combination of resistor 58. potentiometer 59, potentiometer 61 and resistor 63. The junction between potentiometers 59 and 61 is connected to output terminal 17 of operational amplifier 15 and the movable contacts 60 and 62 of respective potentiometers 59 and 61 are .returned to input terminal 16 of the operational amplifier 15 through respective conventional diodes 64 and 65.- By properly adjusting the movable contacts 60 and 62, operational amplifier 15 may produce an output potential of the same magnitude for either polarity. With a positive polarity potential input, the output potential of operational amplifier 15 is of a negative polarity and of a magnitude equal to the potential drop across movable contact 60 and output terminal 17 and with a negative polarity input potential, the potential at output terminal 17 is of a positive polarity and of a magnitude equal to the potential drop across movable contact 62 and output terminal 17. The magnitude of the potential across either of movable contacts 60 or 62 and output terminal 17 will remain substantially constant regardless of the magnitude of the input potential present upon input terminal 16.

Specifically, with a positive polarity input, the output potential of operational amplifier 15 is of a negative polar ity, and of sufiicient magnitude to cause diode 64 to be forward biased and conductive. This causes contact 60 to be electrically linked to amplifier input 16, creating a low-resistance feedback path from amplifier output 17 to input 16, reducing the amplifier gain to near zero, preventing any incre-ase in amplifier output for input signals of greater positive magnitude. Diode 65 is reverse-biased and nonconductive when output 15 is negative. Should the input polarity change from positive to negative, the output polarity will change from negative to positive, during which neither diode 64 nor diode 65 is conductive, eliminating negative feedback and causing great amplification of the input signal, until the output voltage is sufiiciently positive to cause conduction of diode 65, when the gain of the amplifier network again drops to near zero.

To produce the feedback signal, a third voltage divider network comprising the series combination of resistor '76. potentiometer 71 and resistor 73, connected across the positive and negative polarity terminals of the power supply, and a type PNP transistor 50, is provided. The collector electrode 53 of transistor 50 is connected to junction 56 between potentiometer 71 and resistor 73 and the emitter electrode 52 of transistor 50 is connected to point of reference or ground potential 5. Therefore, the collector-emitter electrodes of type PNP transistor 50 are forward poled. The base electrode 51 of transistor 50 is connected to junction 66 between resistor 67 and diode 68 connected in series between output terminal 17 of operational amplifier and point of reference or ground potential 5. Movable contact 72 of potentiometer 71 is connected to point of reference or ground potential 5 through potentiometer 35.

The emitter electrode 32 of type PNP switching transistor 30 is connected to point of reference or ground potential 5 and the collector electrode 33 thereof is connected to the negative polarity terminal of the power supply through a resistor 75 and the filament of indicator lamp 25. Therefore, the emitter-collector electrodes of this type PNP transistor are forward poled. The base electrode 31 of transistor 30 is connected to output terminal -17 of operational amplifier 15 through a series current limiting resistor 76.

The emitter electrode 42 of type PNP switching transistor 40 is connected to point of reference or ground potential 5 and the collector electrode 43 thereof is connected to the negative polarity terminal of the power supply through a resistor 77 and the filament of indicator lamp 26. Therefore, the emitter-collector electrodes of this type PNP switching transistor are forward poled. The base electrode 41 of switching transistor 40 is connected to the collector electrode 33 of switching transistor 30 through junc tion 80, between resistors 78 and 79, and resistor 78.

With the pickup coil of a magnetic pulse generator type distributor connected across input terminals 12 and 13 and movable contact 19 of selector switch 18 closed to stationary contact 20, the distributor housing is rotated in such a direction that the signal induced in the associated pickup coil is initially of a positive polarity and is applied across the input circuit of operational amplifier 15. As the signal present upon the input circuit of operational amplifier 15 is of a positive polarity, the signal upon the output circuit thereof is of a negative polarity.

This negative polarity signal is applied across the base electrode 31 and emitter electrode 32 of switching transistor 3t} and the base electrode 51 and emitter electrode 52 of transistor 50. As this is the proper potential polarity relationship to produce emitter-base current through type PNP transistors, these devices are triggered to conduction.

With switching transistor 30 conducting, an energizing circuit which illuminates indicator lamp is established, from point of reference or ground potential 5, through the emitter-collector electrodes of switching transistor 30, resistor 75 and the filament of indicator lamp 25 to the negative polarity terminal of the power supply, and the potential upon junction 80 is of a positive polarity.

This positive polarity signal upon junction 80 is applied across the base electrode 41 and emitter electrode 42 of switching transistor 40. As this is not the proper potential polarity relationship to produce emitter-base current through a type PNP transistor, switching transistor 40 is nonconductive.

With transistor 50 conducting, the potential upon junction 56 is substantially at ground potential and the potential upon movable contact 72 of potentiometer 71 is of a positive polarity relative to point of reference or ground potential 5. This positive polarity potential is the feedback signal and is, of course, of the same polarity as that of the last signal present upon the input circuit of operational amplifier 15. A portion of this positive polarity feedback signal, as determined by the setting of movable contact 36 of potentiometer 35, is returned to the input circuit of operational amplifier 15 through the feedback circuit comprising movable contact 35, line 37, resistor 38 and line 39, previously described.

Should the operator interrupt the rotation of the distributor housing, transistor 50 and its associated circuitry essentially memorizes or remembers the polarity of the last signal which was present upon the input circuit of amplifier 15 in the form of the feedback signal and, therefore, the circuitry of this unique static timing instrument is unaffected and will give a true indication when the distributor housing is again rotated in the same direction.

As the operator continues to rotate the distributor housing, the signal induced in the pickup coil passes through the cross-over and, therefore, the polarity reverses to negative.

With a negative polarity input signal present upon the input circuit of operational amplifier 15, a signal of a positive polarity is present upon the output circuit thereof and is applied across the base-emitter electrodes 31 and 32 of switching transistor 30 and 51 and 52 of transistor 50.

As this is not the proper potential polarity relationship to produce emitter-base current flow through type PNP transistors, these devices are biased nonconductive.

With switching transistor 30 nonconductive, the energizing circuit for indicator lamp 25 is interrupted, therefore, indicator lamp 25 extinguishes, and the potential at junction is of a negative polarity. This negative polarity potential is applied across the base electrode 41 and emitter electrode 42 of switching transistor 40. As this is the proper potential polarity relationship to produce emitter-base current flow through a type PNP transistor, switching transistor 40 conducts.

With switching transistor 40 conducting, an energizing circuit which illuminates indicator lamp 26 is established from point of reference or ground potential 5, through the emitter-collector electrodes of switching transistor 46, resistor 77 and the filament of indicator lamp 26 to the negative polarity terminal of the power supply.

Therefore, at the. instant of cross-over, from a positive polarity to a negative polarity, of the signal induced in the pickup coil of the magnetic pulse generator type distributor, indicator lamp 25 is extinguished and indicator lamp 26 is illuminated to give a precise visual indication that the distributor is in proper timed relationship with the associated engine.

When used with conventional breaker contact type distributors, input terminals 10 and 11 are connected in parallel with the breaker contacts or points and movable contact 19 of selector switch 18 is closed to stationary contact 21.

While the breaker contacts are closed, the potential at junction 48 is of a positive polarity and is applied across the input circuit of operational amplifier 15. As the signal present upon the input circuit of amplifier 15 is of a positive polarity, the signal at the output circuit thereof is of a negative polarity and, therefore, indicating lamp 25 is illuminated in a manner previously described in regard to the magnetic pulse generator type distributor.

As the distributor housing is rotated, at the instant of opening of the breaker contacts, the polarity of the potential present upon junction 48 goes negative, resulting in a positive polarity signal upon the output circuit of operational amplifier 15. This positive polarity output signal operates in the same manner as that described in reference to the magnetic pulse generator type distributor to extinguish indicating lamp 25 and to illuminate indicating lamp 26.

From this description, it is apparent that the unique static timing instrument of this invention produces a visual indication of the precise instant of cross-over, from a positive polarity to a negative polarity, of the signal induced in the pickup coil of magnetic pulse generator type distributors and the precise instant that the breaker contacts of a conventional breaker contact type distributor open.

It is to be specifically understood that the unique static timing instrument of this invention is not to be construed as limited only to a visual indication as audible or other type indicating devices may be. employed without departing from the spirit of the invention.

Specific transistor types and polarities have been described in this specification for the purpose of clearly describing the operation of the unique static timing instrument. It is to be specifically understood that alternate transistor types and compatible polarities and alternate. switching devices may be substituted therefor.

What is claimed is as follows:

1. A static ignition timing instrument for internal combustion engines comprising, an operational amplifier having input and output circuit means and being of the type responsive to a signal of either polarity upon said input circuit means to produce a signal of opposite polarity upon said output circuit means, means for producing a feedback signal of a polarity the same as the last signal present upon said input circuit means of said operational amplifier in response to a signal upon said output circuit means, feedback circuit means for returning said feedback signal to said input circuit means, first indicator circuit means which may be energized in response to a selected one polarity signal present upon said output circuit means of said operational amplifier and deenergized in response to an opposite polarity signal present upon said output circuit means of said operational amplifier and second indicator circuit means which may be energized in response to the deenergization of said first indicator circuit means.

2. A static ignition timing instrument for internal combustion engines comprising, a source of direct current potential, first and second input circuit means, an operational amplifier having input and output circuit means, selector switch means for selectively connecting said first and second input circuit means to said input circuit means of said operational amplifier, means for producing a feedback signal of a polarity the same as the last signal present upon said input circuit means of said operational amplifier in response to a signal upon said output circuit means of said operational amplifier, feedback circuit means for returning said feedback signal to said input circuit means of said operational amplifier, first and second indicator lamps, first and second controllable switching devices each having at least two current carrying electrodes and a control electrode, means for connecting said current carrying electrodes of said first controllable switching device in series with said first indicating lamp across said source of direct current potential, means for connecting said control electrode of said first controllable switching device to said output circuit means of said operational amplifier, means for connecting said current carrying electrodes of said second controllable switching device in series with said second indicating lamp across said source of direct current potential and means for connecting said control electrode of said second controllable switching device to one of said current carrying electrodes of said first controllable switching device.

3. A static ignition timing instrument for internal combustion engines as described in claim 2 wherein said first and second controllable switching devices are transistor devices.

References Cited UNITED STATES PATENTS 2,536,527 1/1951 Appel 340-332 K THOMAS B. HABECKER, Primary Examiner CHARLES M. MARMELSTEIN, Assistant Examiner US. Cl. X.R. 

